An Upgrade to My Gainclone Amplifier

Well, it is actually an additional pair of LM3886T chip amplifier, which I ordered again through a local supplier for the same amount of money (IDR 150000 or US$16.70). I previously made 4 markings for the drill holes because I wanted to make two pairs of amps, but since I only have a pair, I drilled two holes first to mount the ICs in the middle of the heatsink. So basically I just have to add two more drillholes and that’s it.

Two pairs of bridged amps 😉

Side view

The old and new pairs are both configured for bridge mode operation into 6Ω speakers for 2 channels. This is simply achieved by using just one 100kΩ resistor from one of the LM3886 output pin to the other LM3886’s inverting input pin. As usual, more info on bridging amplifiers can be found in the Wikipedia.

Oh, by the way I have also modded the PSU that powers the amp too! I replaced the 2200μF 35V caps on the filtering side to a pair of 6800μF 50V ones because those smaller caps bulged! This is becoming an obnoxious issue nowadays. Many blogs and articles made mention of bulging capacitors countless times, mainly because of bad manufacturing practice. Heck even Wikipedia has an entry about it too.

New caps for the PSU

One incident happened though, after I replaced the caps. In the above image one of the IRFZ44N mosfets is missing, it blew up! The incident happened just after I increased the amp volume to about 60%. I think the current transient and its associated heat are exacerbating the positive temperature coefficient characteristic of the MOSFET.